Energy saving exit sign retrofit lighting system using light emitting diodes

ABSTRACT

The present invention relates to an exit sign retrofit lighting system kit including a low profile switch mode power supply contained in internal and external enclosure and use Light Emitting Diodes with long life. The system is powered by a high energy efficient switch mode power supply with low power consumption. The height of this lighting system is very close to half of one inch or less. This kit can be used to save energy in existing Exit Sign fixtures using Tungsten filament lamps or linear fluorescent lamp or compact fluorescent lamp. This kit can be also used with Box type and Edge lit Exit Signs. The long life time of Light Emitting Diodes makes it practically maintenance free, in addition to saving considerable energy.

DETAILS OF THE DRAWINGS

FIG. A shows the front view of a double sided Exit sign containing theRetrofit LED kit. The LED driver is mounted inside the LED Fixture.

The LED light fixture is mounted at the center for uniform lightdistribution in the Exit Sign.

FIG. B shows the front view of a double sided Exit sign containing theRetrofit LED kit. The LED driver is mounted external to the LED Fixtureon the side as shown.

The LED light fixture is mounted at the center for uniform lightdistribution in the Exit Sign.

FIG. C FIG. A shows the front view of a Single sided Edge lit Exit signcontaining the Retrofit LED kit. The LED driver is mounted inside theLED Fixture.

The LED light fixture is mounted at the center for uniform lightdistribution in the Exit Sign.

FIG. D shows the front view of a Single sided Edge lit Exit signcontaining the Retrofit LED kit. The LED driver is mounted outside onthe top portion of the Exit sign box container.

The LED light fixture is mounted at the center for uniform lightdistribution in the Exit Sign.

FIG. E shows the front view of a double side Exit sign containing theRetrofit LED kit. This has a battery back up system wherein the Batterypowers the Low voltage Tungsten Filament lamps under power failurecondition. The battery could be mounted any where inside and becomes anintegral part of the system. When the power is “ON”, the battery getsTrickle charge through a charging circuit.

The LED light fixture is mounted at the center for uniform lightdistribution in the Exit Sign. The external push switch as shown is tosimulate the power failure condition to check proper operation underpower failure.

FIG. F shows the front view of a double sided Exit sign containing theRetrofit LED kit with an externally mounted LED driver as shown. Thishas a battery back up system wherein the Battery powers the Low voltageTungsten Filament lamps under power failure condition. The battery couldbe mounted any where inside and becomes an integral part of the system.When the power is “ON”, the battery gets Trickle charge through acharging circuit The external push switch as shown is to simulate thepower failure condition to check proper operation under power failure.

The LED light fixture is mounted at the center for uniform lightdistribution in the Exit Sign.

FIG. G shows the front view of a double sided Exit sign containing theRetrofit LED kit with an externally mounted LED driver as shown. Thishas an electronic inverter to convert the low battery voltage to asuitable high voltage, typically about 28 Vdc to power the LED fixture.The inverter also trickle charges the battery when the main power is“ON”.

The LED light fixture is mounted at the center for uniform lightdistribution in the Exit. The external push switch as shown is tosimulate the power failure condition to check proper operation underpower failure.

FIG. H G shows the front view of a double sided Exit sign containing theRetrofit LED kit with an internally mounted LED driver as shown. Thishas an electronic inverter to convert the low battery voltage to asuitable high voltage, typically about 28 Vdc to power the LED fixture.The inverter also trickle charges the battery when the main power is“ON”.

The LED light fixture is mounted at the center for uniform lightdistribution in the Exit. The external push switch as shown is tosimulate the power failure condition to check proper operation underpower failure.

FIG. I shows the way in which the Light Emitting Diodes are wired inseries and parallel.

FIG. J shows the way in which the Light Emitting Diodes are laid on aprinted wiring board for better light distribution.

FIG. K shows schematic (Circuit diagram) of the design of the LightEmitting Diode driver circuit.

Energy Saving Exit Sign Lighting Retrofit System Using Light EmittingDiodes

BACKGROUND OF THE PREFERRED EMBODIMENT

The present invention is specifically designed for the replacement ofTungsten filament lamp or Compact Fluorescent lamps also known as CFLlamps like one or two F8T5, PL9W or PL13W.

A light-emitting diode (LED) is a semiconductor device that createslight using solid-state electronics. A diode is composed of a layer ofelectron rich material separated by a layer of electron deficientmaterial which forms a junction. Power applied to this junction excitesthe electrons in the electron rich material leading to photon emissionand the creation of light. Depending on the chemical composition of thesemiconductor layers, the color of light emission will vary within thevisible range of electromagnetic spectrum.

LED's are much more energy efficient than their incandescentcounterparts for several reasons. LED's produce uniform light dispersionand light output is dispersed evenly over the lens which make thembrighter than incandescent lamps. LED's are very energy efficientproducing up to 90 percent light output with very little heat whileincandescent bulbs use up to 90 percent of their energy generating heat.Incandescent lamps only produce white light which must be filtered fortraffic signal use, and this leads to an additional loss in energy.LED's, on the other hand, produce colored light that does not need to befiltered out—all of the energy is concentrated around one color band andnone is “wasted” on undesired colors.

The benefits of LED lighting technology includes features such as energysavings, long service life, high quality light, and cold temperatureoperation. In addition to these benefits, LED's do not contain anymercury or lead and have no glass to break.

LED's presently use compound semiconductors. The color of the light isdetermined by the bandgap of the semiconductor. LED's using AllnGaPcompound semiconductor alloys can emit in the yellow-red spectrum, whileLED's using AllnGaN compound semiconductor alloys can emit in theUV-blue-green spectrum. A combination of red, green, and blue LED's, ora blue or UV LED with phosphors can be used to create white light.

The Light Emitting Diode emits electromagnetic wave in the visiblespectrum of the electromagnetic spectrum.

The forward voltage and the necessary current are provided by the powersupply system. A simple power supply system provides power for 56 orless Light Emitting Diodes. Typically the LED's are arranged in seriesand parallel configuration as shown in FIG. I and laid out in PrintedWiring Board FIG J. Generally there are 2 types of power supplies,magnetic and electronic switch mode. In this lighting system, the switchmode electronic power supply is used for energy efficiency, low profile,light weight, and a high power factor.

While a preferred embodiment has been shown, modifications and changesmay become apparent to those skilled in the art which shall fall withinthe spirit and scope of this invention. It is intended that suchmodifications and changes be covered by the attached claims.

LED's do not contain mercury and is environment friendly.

The simplicity of the power supply using very few components greatlyimproves the reliability of this lighting system kit.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Refer to Fig. J.

The 56 LEDs put out enough light output to replace linear F8T5 lamp orCFL 9W as shown in FIG J.

The number 56 is arbitrary and so chosen to be cost effective. Thesenumbers could change depending on growth LED technology resulting incost reduction with higher lumens per watt LEDs.

The design of the power supply is so chosen to put out 42 Vdc maximumand still come under Class 2 requirements of Underwriters Lab standards,UL 1310 for enhancement of safety.

Refer to FIG. K.

Transformer T1 steps down the high input voltage pulses to low voltagepulses.

The power supply has an input stage filter network consisting of a metaloxide varistor, RV1 rated 150V for surge suppression, a safety currentlimiting fuse, F1 rated ½ A 250 Vac, and an across the line capacitorC15, rated 22 P.Fd. 250V to absorb the transients.

The second stage is a full wave bridge rectifier consisting of fourIN4007, D1-D4 diodes, rated 1 Amp. 400V with a filter capacitor rated4.7M.Fd., 400V.

The third stage feeds the rectified AC voltage to an integrated chip IC1THX203X circuit which determines the pulse width after converting therectified voltage to high frequency chopped voltage.

The diode D7 rated 1 Amp. 400V, rectifies to DC voltage is coupled toresistor R10 rated 5.1 ohms.

The output filter network consists of a resistor R12 rated 10 Ohmscoupled to a capacitor C12 rated 680P. Fd., 150V in series coupled tocapacitors C8, C6 rated 220M.Fd. 35V to smooth out the ripple voltage.Capacitor C13 rated 104 P.Fd, 50V further smoothes out the outputvoltage wave shape closer to DC with least amount of ripple. Outputchoke L1 is coupled between C7 capacitor and diode D7 further storesmagnetic energy to provide a constant output voltage.

Resistor R11 and rated 44K ohms with a series choke L2 and a parallelcapacitor rated 470M.Fd.25V forms the output filter network.

There is a feed back circuit consisting of resistor R8 rated 38.3K. Ohmscoupled to IC2, TL 431A which is an adjustable reference zener diode.This zener is coupled to the power supply through a resistor R10, R11rated 5.1K Ohms and 44 K ohms respectively.

The turn on reference voltage is determined by R11 and R10 Ohms coupledto capacitors C6, C8 rated 220 M Fd. 50V.

When the output exceeds the set voltage, the IC2 turns on providing asignal to Opto Isolator U1, model PC817 through U3, the adjustablereference zener diode model TL 431 to the pin 9 of the control IC U2 bycharging the capacitor C10 rated 22 P Fd, 50V.

Capacitor C9 rated 68 P.Fd. 50V provides the timing frequency foroscillations.

Diode D5 rated, IN 4007 coupled with transformer and capacitor C4 rated47 M.Fd., 16V provide start up current for the transformer oscillations.

Capacitor C13, rated 10 P.Fd, 50V is coupled to ground to absorb thetransient voltages appearing across the output.

Capacitor C7 rated 100 M Fd, 35 V provides necessary filtering of theoutput voltage to reduce the output ripple.

Refer to FIG. K—marked T1

The processed signal is fed to the transformer T1 made out of ferritecore with the following construction.

Primary Windings:

Wind 18T on the magnet core EFD15 From Pin 1 to Pin 3 by 0.15 mm enamel.

Secondary Windings:

Wind 135T on the magnet core EFD15 FROM Pin 2 to Pin 4 by 0.2 mm enamel.

Wind 32T on the magnet core EFD15 FROM Pin 8 to Pin 5 by 0.2 mm×3enamel.

1. A preferred embodiment of exit sign lighting retrofit systemcomprising: A power isolated supply circuit marked as 3 in FIG. A,electrically coupled to the LED arrays with a means to provide power tothe LEDs in such a manner that the system is characterized by an inputpower factor of at least 90%.
 2. The lighting system has an array ofLEDs connected in series and parallel combination in plural quantitymounted on a printed wiring board as shown in FIG. I and FIG. J for thebest light distribution.
 3. An aluminum extruded body marked as 1 inFIG. A serves the purpose of holding LED arrays and power supply inposition as marked 4 and 3 respectively as shown in FIG. A.
 4. The LEDhousing is secured by Quick Connect clips as marked in 2 and 5 in FIG.A.
 5. The Exit sign indicators slide out through notch marked as 8 and 9in FIG. A. The overall enclosure is marked as 10 in FIG. A. FIG. B showsan alternate arrangement of FIG. A where the Power supply 13 and itshousing 14 are to the LED board 12 externally connected.
 6. FIG. C showsan alternate arrangement of FIG. A where the retrofit kit is used withEdge Lit system. The hosing is marked as 15, input wires are marked as16, spring loaded locking is marked as 19, the closing cover is markedas 17 and the Exit Sign is marked as
 18. The input power to the LEDpower supply is provided by directly connecting to the input mains byquick connect terminals and wire nuts. FIG. D is an alternatearrangement of FIG. C where the Power supply contained in its enclosureare marked 21 and 22 respectively and mounted as shown.
 7. An energyefficient internal low profile, typically about 13 mm height powersupply with high power factor to provide the necessary voltage and apredetermined constant current to power the LEDs marked as 14 in FIG. B.The constant current typically 20 ma. provides uniform light intensitywhich is very critical.
 8. The LED arrays are so shaped and formed toprovide uniform light output in the entire exit fixtures as shown inFIGS. A, B C and D.
 9. The LEDs are so chosen that the inner and outerarray has 120 degrees spread for uniform illumination.
 10. Electricalsurge protection is provided by the power supply by means of a metaloxide varistor or transorb or gas filled tube or the combination ofmetal oxide varistor in parallel with a disc capacitor connected acrossthe input power as marked Rv1 in FIG. K. This prevents blow out of theEXIT Signs during thunder storms.
 11. This kit can be used to saveenergy, about 80 percent, in Exit Sign fixtures described thus far, onefor “ Box light system” as shown in FIG. A and “edge lit” FIG. C. 12.This kit can also be used in Exit Signs with Battery Backup systems incase of Power Failures. Refer to FIG. E And FIG. F. In FIG. E, thebattery is marked as 22, housing is marked as 23, the LED module withintegral power supply marked as 24, interconnections as marked as 25,enclosure is marked as 26, and the Exit sign is marked as
 27. Lowvoltage battery operated tungsten filament lamps are marked as 28 and 29when there is a power outage. FIG. F is an alternate variation of FIG. Ewhere the power supply is mounted externally as shown. The test switchmarked as 34 is used to test the unit by depressing the switch tosimulate the power outage.
 13. This kit can be used to save energy inExit Sign fixtures described in FIG. G where the power supply 37 and itshousing 36 are mounted external to the unit. The battery 43 is to coupleto the invertor 39 through a transformer 38 in order to boost the lowvoltage battery to 120 Volt to power the LED Power supply module topower the Exit Sign during the power outage. The button test switchmarked as 41 to simulate the power outage condition for testing beforeinstallation. Another LED indicator marked as 42 is to indicate thecharging of the battery. The enclosure is marked as
 40. FIG. H is analternate arrangement of FIG. G where the LED power supply is integralto the LED power module.
 14. When used in the Battery Back up system,during the Power Outage the Light Emitting Diodes operate from theBattery power with much less energy thereby prolonging the battery powerconsiderably by staying lit at least for 4 hours offering extra marginof safety exceeding the minimum requirements of 90 minutes required byUnderwriters Lab Standard
 924. 15. With this LED retrofit kit, the LEDsare optimally spaced for diffused lighting to meet the contrast ratioset by Underwriters Lab Standard
 924. 16. In this LED retrofit kit, thebrightness of LEDs remain more or less constant because of constantcurrent supplied to the LEDs as compared to the Fluorescent lamps andtungsten filament lamps where the light intensity goes down during therequired 90 minutes of operation during a power outage.
 17. With thisLED Retrofit kit, by increasing slightly the Amp Hr. capacity of thebattery used, the LEDs stay lit for about 8 hours offering additionaloption.
 18. This Retrofit kit makes the Exit Sign fixture practicallymaintenance free for approximately 5 years saving Labor and lampreplacement costs.
 19. With this LED retrofit kit, since there are nostarters involved, there is no annoying flickering of Fluorescent lamps.20. With this LED retrofit kit, there is an added advantage of startingLEDs even under cold environment like 40 Deg. F unlike starting problemsassociated with Fluorescent lamps at very low temperature.
 21. SinceExit Sign stays lit 24 hours a day, 365 days a year, in addition toenergy savings it also minimizes or even eliminates violation noticesfrom the city inspectors and penalties for Exit Sign not being litduring power outages because of non functional lamps.
 22. With this LEDretrofit kit, the LEDs are so chosen to produce a uniform Day lighttypically producing a color temperature of 5000 Deg. K. for readyvisibility. Depending on application requirements the color temperatureof the LEDs can be chosen in the range of 2700 Deg. K and 6000 Deg. K.23. With this LED retrofit kit, installation in the field is very easy,typically takes less than 10 minutes in the Exit Signs with or withoutbattery back up which in turn leads to considerable labor cost savings.24. With this LED retrofit kit containing the long life of LEDstypically 50,000 hours or more, there will be practically no need todispose of hazardous materials like mercury contained in compact ortubular fluorescent lamps used in existing Exit Signs.